LT1 Cooling fans???
LT1 Cooling fans??? So, recently picked up my 96 Z28 w 28K original miles. It has sat in a barn for the past 12+ years driven short distances occasionally.
Cooling fans will not come on while sitting or driving... While running unplugged sensor in WP to see if fan would engage. 1 did.. It comes on and runs. Also replaced radiator cap. Temp creeps up to 230+ so I shut down ( am not driving it) Trying to trouble shoot what it could be. So, in the fuse box under the hood there are 3 relay for 3 fans?? I can only get one to come on when sensor unplugged.
The coolant looks BAD!! Wondering if the to T stat is froze up or if I should replace water pump, t stat, coolant altogether....?
Regarding temp gauge in car... Its low at first ( obviously) Doesn't take long to shoot up there while just idling... Other times I have driven it 6-7 miles and its under 210 degrees .. Once I stop for a few min.. the temp creeps up to 230... Then I shut it off... I cannot get these fans to come on. I have looked at all of the wiring, fans are plugged in...
Ok... lets hear your thoughts, suggestions...
I have read about jumping off relay w paper clip but I have never done that before... don't want to short anything out.
Cooling fans will not come on while sitting or driving... While running unplugged sensor in WP to see if fan would engage. 1 did.. It comes on and runs. Also replaced radiator cap. Temp creeps up to 230+ so I shut down ( am not driving it) Trying to trouble shoot what it could be. So, in the fuse box under the hood there are 3 relay for 3 fans?? I can only get one to come on when sensor unplugged.
The coolant looks BAD!! Wondering if the to T stat is froze up or if I should replace water pump, t stat, coolant altogether....?
Regarding temp gauge in car... Its low at first ( obviously) Doesn't take long to shoot up there while just idling... Other times I have driven it 6-7 miles and its under 210 degrees .. Once I stop for a few min.. the temp creeps up to 230... Then I shut it off... I cannot get these fans to come on. I have looked at all of the wiring, fans are plugged in...
Ok... lets hear your thoughts, suggestions...
I have read about jumping off relay w paper clip but I have never done that before... don't want to short anything out.
Nothing …. ? Guess i'll try replacing the relays....?
Just bought 3 new relays... Process of elimination....
Lets just say the t stat is not opening.... that shouldn't have anything to do with the fans coming on yes? I just drove the car up the street about 5 miles and she never got hot... BUT the fans never came on... Once I got home and idled for a few the temps rose.. no fans...?
I should have those relays by Monday... Til then i'll tackle the EGR valve and do some more cleaning...
Just bought 3 new relays... Process of elimination....
Lets just say the t stat is not opening.... that shouldn't have anything to do with the fans coming on yes? I just drove the car up the street about 5 miles and she never got hot... BUT the fans never came on... Once I got home and idled for a few the temps rose.. no fans...?
I should have those relays by Monday... Til then i'll tackle the EGR valve and do some more cleaning...
Last edited by 01Z0H6; Mar 19, 2019 at 06:11 PM.
Seeing as the car sat for 12 years and you stated the coolant looked bad, I would start with a full cooling system flush. Drain and run water and a cleaner through it and then drain everything out. Open the block drains and flush water through the motor, unhook the hoses and flush the radiator and heater core too. It's probably pretty caked up in there from sitting with old coolant and that may prevent the sensor from triggering the fans. Considering the age of all the components, change the pump, stat and hoses while you're at it.
As far as the relays, they are usually triggered by a ground signal. Find which relay wire/terminal is the ground and jump that to a good ground and fans should come on.
As far as the relays, they are usually triggered by a ground signal. Find which relay wire/terminal is the ground and jump that to a good ground and fans should come on.
Joined: Nov 2003
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From: Jacksonville, FL (originally from Toronto Canada)
There are only two fans. The three relays are wired together in a sequence that causes both fans to run at half speed when only relay #1 is active. That sends power through fan #1, relay#2 (at rest), and then fan #2. Since both fans are running on a single circuit, the load is doubled and the fans run at half speed. When relays #2 and #3 are activated by the PCM, power flows through fan #1 to ground allowing it to run at full speed. At the same time, relay#3 provides power directly to fan #2 and to ground allowing it to run at full speed as well.
As Z28 6spd mentioned, the relays are controlled by ground connections at the PCM. If you ground the dark green wire coming from relay #1, both fans should run at low speed. If not, first check the two fan fuses (labeled COOL FAN) in the underhood junction box (one is 40A to power the fans and the other is 10A to power the relays). If the fuses are okay then you could have a problem with one or more of the three relays, the fans themselves, or the wiring between them. If the fans work when you ground the dark green wire then you have a problem with the wiring between the relays and the PCM or with the PCM itself.
As Z28 6spd mentioned, the relays are controlled by ground connections at the PCM. If you ground the dark green wire coming from relay #1, both fans should run at low speed. If not, first check the two fan fuses (labeled COOL FAN) in the underhood junction box (one is 40A to power the fans and the other is 10A to power the relays). If the fuses are okay then you could have a problem with one or more of the three relays, the fans themselves, or the wiring between them. If the fans work when you ground the dark green wire then you have a problem with the wiring between the relays and the PCM or with the PCM itself.
Thank you both for the feedback ALL great info. Since I posted I have ordered a new GM Delco Water pump, new T stat, 3 new relays, new radiator cap, new overflow jug w hose ( the one on it had been chewed in two and fused back together w a plastic "t" in the hose ends" It looks to be obstructing flow from radiator neck to overflow. So I just bought another one. Regarding overflow tank, the coolant is clear in it.. NO GUNK on the level indicator. ( good thing). So much to do, so little time... I should be able to get on this in a couple of weeks.
I checked fuses and all is good. Also replaced the temp sensor in WP.
I checked fuses and all is good. Also replaced the temp sensor in WP.
http://shbox.com/1/fan_schematic_1995.jpg As the others have said, flush the coolant and then you can check the operation of the fans manually by grounding one of the wires at connector 100. http://shbox.com/1/fan_sw_diagram1.jpg
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TECH Regular
Joined: May 2014
Posts: 440
Likes: 22
From: Houston Texas
Get the SLP fan switch to bypass the relays at will. They can still operate normally, if there is nothing wrong with the car. IE, PCM problem, sensor problem, relay problem, etc etc. You can leave the switch off, and everything works fine. If they dont work at all, this will allow you to manually turn both on low or full speed or off. It really helps with cooling issues as these fans dont work correctly most of the time. SLP switch fixed all my over heating issues, well, after a new water pump, heater core, hoses, tstat, and radiator. After all that stuff, fans still would not kick on until 230-240 degrees. And would only stay on until it dropped to 210ish. Never found the problem, said **** it after the SLP switch because never over heated again.
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You don't need a manual fan switch. First of all, 230 is not at all unusual for a stock LT1. The high speed fans aren't even commanded until 235 degrees with stock programming. You mentioned that one fan came on when you disconnected the WP temp sensor. Both should be on, so you have a bad fan or faulty wiring. The diagrams and diagnostic procedures for wiring have been provided in previous posts, start there. If the wiring checks out, you have a bad fan.
Since this car has sat for so long, you would do very well to give it a full tune up. Here's plenty of reading regarding the cooling system. Shoebox's website has many excellent LT1-specific articles and resources.
http://shbox.com/1/4th_gen_tech2.html#cooling
Since this car has sat for so long, you would do very well to give it a full tune up. Here's plenty of reading regarding the cooling system. Shoebox's website has many excellent LT1-specific articles and resources.
http://shbox.com/1/4th_gen_tech2.html#cooling
TECH Regular
Joined: May 2014
Posts: 440
Likes: 22
From: Houston Texas
You don't need a manual fan switch. First of all, 230 is not at all unusual for a stock LT1. The high speed fans aren't even commanded until 235 degrees with stock programming. You mentioned that one fan came on when you disconnected the WP temp sensor. Both should be on, so you have a bad fan or faulty wiring. The diagrams and diagnostic procedures for wiring have been provided in previous posts, start there. If the wiring checks out, you have a bad fan.
Since this car has sat for so long, you would do very well to give it a full tune up. Here's plenty of reading regarding the cooling system. Shoebox's website has many excellent LT1-specific articles and resources.
http://shbox.com/1/4th_gen_tech2.html#cooling
Since this car has sat for so long, you would do very well to give it a full tune up. Here's plenty of reading regarding the cooling system. Shoebox's website has many excellent LT1-specific articles and resources.
http://shbox.com/1/4th_gen_tech2.html#cooling
2 years ago, I was able to find plenty of SLP switches, but they were discontinued. Figured they would still be in stock. I cant find **** either with some quick searching.
http://www.xious.com/camaro/install-fanswitch.html
Basically same thing, but if you wanted to do the SLP full knock off, you just find some connectors in a junk yard or something. Instead of tapping into the connectors, potentially damaging them.
Thank you Spartan...
Working on all of that.
Working on all of that.
You don't need a manual fan switch. First of all, 230 is not at all unusual for a stock LT1. The high speed fans aren't even commanded until 235 degrees with stock programming. You mentioned that one fan came on when you disconnected the WP temp sensor. Both should be on, so you have a bad fan or faulty wiring. The diagrams and diagnostic procedures for wiring have been provided in previous posts, start there. If the wiring checks out, you have a bad fan.
Since this car has sat for so long, you would do very well to give it a full tune up. Here's plenty of reading regarding the cooling system. Shoebox's website has many excellent LT1-specific articles and resources.
http://shbox.com/1/4th_gen_tech2.html#cooling
Since this car has sat for so long, you would do very well to give it a full tune up. Here's plenty of reading regarding the cooling system. Shoebox's website has many excellent LT1-specific articles and resources.
http://shbox.com/1/4th_gen_tech2.html#cooling
I actually found a guy last night on FB Marketplace out In San Diego... He was selling a brand new one back in 2016... Did not show that it was sold.. Took a gamble, reached out, he still has it... lol Brand new never used.. $55 shipped to me here in Dallas... Big score...
Spartan, I may in fact have a bad fan.... I have since drained the coolant, replaced T stat, relays, GM Delco coolant temp sensor (WP).. Waiting on a new Coolant overflow jug ( Varmant ate the hose down by battery) hoping to have it today, Monday...
I'll post results once I figure it out... Thank you for all of your feedback.
Spartan, I may in fact have a bad fan.... I have since drained the coolant, replaced T stat, relays, GM Delco coolant temp sensor (WP).. Waiting on a new Coolant overflow jug ( Varmant ate the hose down by battery) hoping to have it today, Monday...
I'll post results once I figure it out... Thank you for all of your feedback.
I only disagree depending on where you live. Im in Houston, 230 is too high for cruising around here during the summer. Given traffic, heat, humidity, over 220 is usually a death sentence for these if everything is not in tip top form. Which, being 23+ years old, this becomes more of an issue. Everything was good cooling system wise on mine, and if it stayed at 220, everything was good. Low speed fans were on, but if it got hot enough to turn the high speed on, it would not cool off. It would act like it was going to, then steady rise back up and hover right under red.
2 years ago, I was able to find plenty of SLP switches, but they were discontinued. Figured they would still be in stock. I cant find **** either with some quick searching.
http://www.xious.com/camaro/install-fanswitch.html
Basically same thing, but if you wanted to do the SLP full knock off, you just find some connectors in a junk yard or something. Instead of tapping into the connectors, potentially damaging them.
2 years ago, I was able to find plenty of SLP switches, but they were discontinued. Figured they would still be in stock. I cant find **** either with some quick searching.
http://www.xious.com/camaro/install-fanswitch.html
Basically same thing, but if you wanted to do the SLP full knock off, you just find some connectors in a junk yard or something. Instead of tapping into the connectors, potentially damaging them.
I live in Houston, same as you. I used to daily drive mine when I was stationed in the desert, in 120 degree heat, and it was no big deal. I've also had an SLP fan switch in the past, and all it does is potentially drain your battery if you forget to turn it off. If you want yours to run cooler, have the fans reprogrammed. Mine runs at 185 all day long no matter how hot it is outside with the factory fans and radiator. A fan switch is only a bandaid to his problem, you shouldn't be suggesting it at this point. Fix the problem, then you can put whatever you want on there.
I too have been to a few different deserts... 32 years Army...
I live in Houston, same as you. I used to daily drive mine when I was stationed in the desert, in 120 degree heat, and it was no big deal. I've also had an SLP fan switch in the past, and all it does is potentially drain your battery if you forget to turn it off. If you want yours to run cooler, have the fans reprogrammed. Mine runs at 185 all day long no matter how hot it is outside with the factory fans and radiator. A fan switch is only a bandaid to his problem, you shouldn't be suggesting it at this point. Fix the problem, then you can put whatever you want on there.
TECH Regular
Joined: May 2014
Posts: 440
Likes: 22
From: Houston Texas
Dry heat is easy to deal with. Thermal dynamics works better actually.
Houston ****** sucks. Deserts, the wind is nice. The shade is nice. Houston, it is all hot. Not matter what. Reprogramming is definitely better way to go than switches, but costs more. If everything is in good working order, Houston is no problem. Im just saying, its a bitch to deal with if not.
I sold my red TA with the SLP switch, a week ago, I found it on craigslist with a blown head gasket. He forgot to turn it on....Lots of variables to deal with when you got the switches. I couldnt find why mine wouldnt cool off once high speed kicked on, switches solved it but introduced other issues. Mainly required me to remember. Everything was good and new, except OE radiator. But it gave no signs of any other issues.
Houston ****** sucks. Deserts, the wind is nice. The shade is nice. Houston, it is all hot. Not matter what. Reprogramming is definitely better way to go than switches, but costs more. If everything is in good working order, Houston is no problem. Im just saying, its a bitch to deal with if not.
I sold my red TA with the SLP switch, a week ago, I found it on craigslist with a blown head gasket. He forgot to turn it on....Lots of variables to deal with when you got the switches. I couldnt find why mine wouldnt cool off once high speed kicked on, switches solved it but introduced other issues. Mainly required me to remember. Everything was good and new, except OE radiator. But it gave no signs of any other issues.
TECH Regular
Joined: May 2014
Posts: 440
Likes: 22
From: Houston Texas
I live in Houston, same as you. I used to daily drive mine when I was stationed in the desert, in 120 degree heat, and it was no big deal. I've also had an SLP fan switch in the past, and all it does is potentially drain your battery if you forget to turn it off. If you want yours to run cooler, have the fans reprogrammed. Mine runs at 185 all day long no matter how hot it is outside with the factory fans and radiator. A fan switch is only a bandaid to his problem, you shouldn't be suggesting it at this point. Fix the problem, then you can put whatever you want on there.
Well said... I would prefer to fix it right... But until such time I can use the SLP fan switch. Now then, if I hook this thing up and the fan/s do not come on... Then i'll replace the fans. Again the car only has 28K miles, pretty sure fans are not seized up. I can spin em freely by hand..
Something I normally agree with, however, the SLP switch, and those mods just like it, allow normal operation. So, STILL fix the problem like you said, but its a nice addition. Fail safe. Cooling issues is the number one thing I see people deal with on these cars. Its an easy bandaid that allows your whip to keep whipping while you figure out whats up.
pop the connector off both fans and use a set of jumper wires to apply power and ground and see if each fan kicks on. I bet you have a bad one, or a wire is busted under where the relays plug in in the relay/fuse center.